超声图像引导定义前列腺癌调强放疗的计划靶区

B-mode ultrasound for defining planning target volume in intensity-modulated radiotherapy for prostate cancer

目的分析超声图像引导摆位系统(B mode acquisition and targeting,BAT)辅助前列腺癌调强放疗时等中心摆位误差,定义无影像引导下前列腺癌调强放疗计划靶区(PTV)的边界。材料和方法选择10例前列腺癌患者每日应用BAT引导摆位进行调强放疗,记录每次等中心前后(AP)、左右和头脚方向上移位的偏差,共255次。采用Kolmogorov-Smimov方法分析检验所获得的数据。结果 BAT验证后等中心移位在左右方向为(3.56±2.71)mm,前后方向(4.08±3.99)mm,头脚方向(3.20±2.92)mm。各个方向上的偏差符合正态分布(RL P=0.806,AP P=0.0.061,SI P=0.106)。在没有图像引导前列腺癌调强放疗摆位的情况下,为满足95%的等剂量曲线覆盖90%患者的CTV,PTV边界需在左右方向向右扩大8.97 mm,向左1.87 mm,前后方向向前需扩大12.05 mm,向后3.91 mm,头脚方向向头侧扩大9.06 mm,向脚侧扩大2.66 mm。结论超声图像引导摆位操作简便,无辐射,系统误差小,可实时纠正。

Objective To define the planning target volume（PTV） margins in intensity-modulated radiotherapy（IMRT） for prostate cancer without imaging guidance using B-mode acquisition and targeting（BAT） ultrasound-based prostate localization.Methods Ten patients with prostate cancer underwent BAT ultrasound alignment before each IMRT session.The set-up deviations,each consisting of isocenter displacements in 3 directions（anterior-posterior, right-left lateral,and superior-inferior）,were recorded for a total of 225 times and analyzed with Kolmogorov-Smimov（K-S） method.Results The isocenter shift in each direction,which represented an average from all the patients,was 3.56±2.71 mm,4.08±3.99 mm,and 3.20±2.92 mm in the lateral（RL）,anteroposterior（AP）,and superior-inferior（SI） dimensions,respectively,and the deviations in each direction conformed to a normal distribution（P=0.806,P=0.061,and P=0.106,respectively）.In the absence of imaging guidance for IMRT for prostate cancer,the PTV margin should expand by 8.97 mm in the right,1.87 mm in the left,12.05 mm in the anterior,3.91 mm in the posterior,9.06 mm in the superior and 2.66 mm in the inferior to allow 95% isodose curve to cover 90% of the clinical target volume.Conclusion The ultrasound imagining guided localization,with simple operation,nonirradiation and small systemic error,can be real-time corrected.